Abstract DVT is the most feared complication of total joint replacement (TJR), with more than 300,000 total hip and 700,000 total knee replacements performed annually in the U.S. Current recommendations for postoperative DVT prophylaxis after TJR include anti-coagulant medications and/or intermittent pneumatic compression (IPC) of the lower limb for a minimum of 10-14 days. Most current IPC devices are non-mobile, making early postoperative mobility, which is especially important in TJR patients, cumbersome and time-consuming. Upon hospital discharge, most patients go home on pharmacologic DVT prophylaxis. Even when at-home external compression therapy is prescribed (IPC or compression stockings), data suggests compliance rates as low as 10-50%. Recovery Force (RF) has produced the next generation of mechanical DVT prophylaxis, with a mobile device absent of tubes and pumps, stays in place during ambulation, is lightweight and comfortable for continuous wear, and is designed to improve compliance with recommended use. The hypothesis for Phase II is that IPC using the RF1400 will result in improved compliance, support early mobility and result in significantly higher functional mobility after TJR as compared to standard of care. As a continuation of the successful completion of Phase I, RF proposes a multi-center trial (N=300) to achieve the following Aims: Aim 1: Optimize the product design based on findings from Phase I SBIR. Several findings as a result of Phase I study have led to a redesigned device, referred to as RF1400 Gen II. These findings include the need for the device to fit in the existing hospital work flows, for calf sleeves to be disposable, a fully optimized battery and the ability to track mobility. Aim 2. Conduct a randomized comparative study of DVT prophylaxis using either standard IPC (Group 1) or the RF1400 (Group 2) in 300 patients after TJR surgery. Dr. Karen Giuliano of Northeastern University will serve as the overall PI for efforts associated with the study sites. This study will include an inpatient phase and an outpatient phase with patients at two clinical sites: Tufts Medical Center and Indiana University School of Medicine, with each site enrolling 150 patients (75 control/75 experimental). Aim 3. Measure patient reported outcomes (PRO) of comfort, device acceptance and ease-of-use. The overall goal of Phase II is to demonstrate that compliance with recommended use, postoperative mobility, and ease-of-use is significantly higher with the RF1400 than with DVT prophylaxis using either standard IPC (in-hospital) or standard-of-care (at-home) in preparation for full commercialization in the TJR market during Phase III. The DVT therapy market is expected to hit $3.8B by 2021, and the US accounts for over 50% of the global market. With the current risk of bleeding from anticoagulant DVT prophylaxis at 5.6%, the commercial impact of this research is that improved patient compliance with the RF1400 DVT prophylaxis will improve postoperative mobility and provide an effective alternative to anticoagulation.